The distribution and variability of the Atchafalaya River plume

The Atchafalaya River discharges an annual average of 14,000 m3s-1 of freshwater and 84 x 10 6 metric tons of suspended sediment to the coastal ocean approximately 220 km west of the Mississippi Delta. This discharge results in a plume of low-salinity water and fine-grained sediment that spreads offshore and westward along the Louisiana coast. A study conducted between October 1997 and March 2001 generalized the plumes into two types: a surface advected and a bottom-attached plume. In the latter, surface and bottom salinity contours generally are parallel to the coastline, the plume is weakly stratified, sediment is suspended throughout the water column, and winds are typically from the southeast. In surface advected plumes, stratification is greater, suspended sediment decreases 40 km from the river mouth, and winds are from north.